Using data from the 1 percent samples of the 1960 and 1970 U. S. Censuses and recent Current Population Surveys we are investigating changing patterns of differential fertility in the U. S. We are analyzing differential fertility at the beginning and end of the 1960's in order to assess the extent to which various subgroups have participated disproportionately in fertility changes and to document the resulting alterations in the nature of differential fertility. We address ourselves to five major issues: (1) Differentials in completed fertility, 1960 and 1970. This is essentially a detailed comparison of subgroup differences in completed fertility for cohorts whose childbearing centered on the periods just before, and near the crest, of the post-war "baby-boom." An important innovation in this analysis is the consideration of differentials in terms of parity progression probabilities. (2) Differentials in "current" fertility. 1960 and 1970. Based on estimates of subgroup fertility over the one to five years preceding each census date (1.e., from the late 1950's and late 1960's), this analysis should document the extent to which various subgroups have participated in recent declines. (3) The fertility of minority groups. Utilizing the opportunities afforded by the greater sample size of the 1 percent sample tapes, we are documenting in detail changes in fertility and in differentials in fertility within and among various minority groups such as blacks, Mexican-Americans, American Indians, Puerto Ricans, farmers, and other groups. (4) The role of differential timing patterns in measured differentials in "current" fertility. Recognizing that period changes can result from changes in the tempo of fertility as well as (or even instead of) changes in the quantity of fertility , we are examining changes in differential patterns of age at first marriage and marital disruption, and in birth intervals. (5) Differential patterns of female employment. As an important intervening "role" factor in fertility, we are examining patterns of labor force re-entry after child-bearing, and several other aspects of changing labor market activity of women.